Downhole systems rely on various valves to control fluid flow. On occasion, it is desirable to introduce a fluid, such as a chemical into a wellbore or other portion of a downhole system. Chemical injection systems typically rely on a normally closed chemical injection valve (CIV). The CIV includes a dart that is biased against a seat through a spring. A preload is applied to the spring prior to introducing the CIV downhole. A liquid is introduced into the CIV at a pressure sufficient to move the dart off the seat against the pressure applied by the spring. Once unseated, the liquid may then flow through the valve.
Once introduced downhole, the preload on the spring cannot be adjusted without withdrawing the CIV from the wellbore. Without modification of the preload, adjustments to liquid pressure are limited. That is, the liquid being introduced into the CIV must be at least at a pressure sufficient to unseat the dart. Withdrawing the CIV is a time consuming and costly process. Adjusting the preload is also a time consuming process requiring cutting the CIV open and then welding it closed. In most cases, if there are issues with the preload, the CIV is simply discarded. Accordingly, once a preload is chosen, operators are limited to a particular pressure floor for the liquid.